Influenza viruses are constantly changing and a person’s immune protection from influenza vaccination declines over time, hence the need for annual shots for optimal protection.
We know that SARS-CoV-2 viruses undergo evolution. Some new virus variants may be associated with higher transmissibility, disease severity, risk of reinfection, or a change in antigenic composition resulting in lower vaccine effectiveness.
WHO and partners undertake a coordinated approach to monitoring and evaluation of variants and their impact on vaccine effectiveness.
We need to do everything we can to reduce circulation of the virus and delay mutations that may reduce the efficacy of existing vaccines. It also seems increasingly clear that manufacturers will have, and are ready, to adjust to the COVID-19 viral evolution, taking into account the latest variants for future booster shots.